1. Field Of the Invention
The present invention relates to a superconducting circuit board and a paste adopted for forming a superconducting ceramic pattern on a ceramic board. Such a superconducting circuit board is useful for a high speed computer such as a supercomputer.
2. Description of the Related Art
The insulating material used for a circuit board for high speed processing must have a low dielectric constant and the conducting material used must have a low electrical resistance, to ensure an efficient transmission of electrical signals. In the prior art, as such a circuit board, a multilayer ceramic circuit board is formed in which copper is used as the conducting material.
Recently, superconducting ceramics such as La-Ba-Cu-O system, La-Sr-Cu-O system, and Y-Ba-Cu-O system which exhibit a superconductivity at the temperature of liquid nitrogen (77 K) have attracted attention and investigations into and developments of such materials are proceeding rapidly. To attain a superconducting circuit substrate, it is essential to develop a technique by which a superconducting ceramic past can be printed on a ceramic board, such as an alumina board used in a hybrid IC, and fired to form an interconnection pattern of a superconductor.
Ceramic boards, including an alumina board, used for a circuit board, generally but except for a complete crystal monolith, have a structure comprising crystal grains, grain boundaries, also called a glass phase, and pores, and the higher the content of the glass phase, i.e., the lower the purity of the ceramic board, the lower the temperature at which the ceramic board can be fired or sintered. As a result, ceramic boards are generally manufactured by adding, to a ceramic, ingredients for a glass phase and able to be fired at about 1500.degree. C. The ingredients for a glass phase are added to lower the firing temperature.
It was found that a fired, compacted body of a superconducting ceramics exhibits superconductivity, but if a pattern of a superconducting ceramic paste on an alumina board is fired to obtain a superconducting ceramic pattern, the resultant fired pattern does not exhibit superconductivity.
Thus, the object of the present invention is to provide a superconducting ceramic film on a ceramic board.